Muscles shine with sweat as boxers beat truck tyres with rudimentary metal bars and punch the only sand bag in a spartan gym.
The headquarters of the Cuban boxing team on the outskirts of Havana has been turned into a boot camp for the country's best fighters heading for August's Athens Olympics.
For inspiration, pictures on the wall include three-time Olympic heavyweight champion Teofilo Stevenson and a young Fidel Castro in military fatigues raising his gloved fists in the air.
A slogan above the ring declares: "In Cuba we only love those who resist and the rest we tolerate".
"Boxing is well suited to the Cuban character: we are brave, resolute, selfless. We have strong convictions and clear definition. We are pugnacious and we like to fight," said coach Alcides Sagarra, the father of Cuba's Olympic successes.
"Some people fight and lose. We fight to win. We are training to take all 11 gold medals in Athens. Thinking small doesn't give results," he said with a smile full of gold teeth.
Cuba has consistently produced some of the world's best amateur boxers, most notably since Castro's 1959 revolution got rid of the "scourge" of professional boxing, "the worst exploitation of man by man" that made some rich and left many boxers battered and poor, Sagarra said.
Cuba have been the most successful boxing team at every Olympic Games since Munich in 1972, with the exception of Montreal in 1976. Their goal is to catch up with arch-rivals the United States, who have won 44 gold medals in boxing since 1904.
Cuban boxers have won 27 golds since Munich, where Stevenson won his first in the 81-kg category. Cuba would have bagged more medals had they competed in Los Angeles in 1984 and Seoul in 1988, when the country joined the boycott by Soviet bloc nations in the final years of the Cold War.
At the Pan-American Games in 1991 in Havana, Cuban boxers swept up 11 of the 12 golds, losing just one to United States.
In 1992, Cubans won seven of the 12 gold medals in Barcelona, with Felix Savon winning the first of his three back-to-back Olympic heavyweight titles.
Savon, who retired after Sydney, and Stevenson are the two Cubans who have entered the elite club of just three boxers to become triple consecutive gold-medal winners. The select group's first member was Hungarian Lazlo Papp. Russia's welterweight champion Oleg Saitov has won two golds and will be looking for his third in Athens.
Cuban officials say Cuba's socialism is the reason behind its athletic achievements. The Caribbean island of 11 million has won more Olympic medals per capita than any other nation. All young Cubans have access to sports and athletes get special treatment, better diets and full-time dedication so they can excel.
"There's no secret to the supremacy of Cuban boxers," said Sarbelio Fuentes, who succeeded Sagarra as head coach. "Our social system guarantees the development of athletes from an early age."
Cuba's African blood and musical rhythms derived from slaves drums contributed to the boxing skill, said trainer Rolando Garbey.
"Our boxers have more dance and movement in the ring. That allows them to defend themselves better and they suffer less, like Muhammad Ali," Garbey said. "European boxing continues to be pure force. We move like salsa dancers."
Outside the gym, boxers work out playing basketball and jog around the school compound. They rise at six a.m. every day and train morning and afternoon for three months, before heading off to Europe to compete in boxing events ahead of the Olympics.
The team's leading lights are Mario Kindelan, who fights in the 60-kg category, and Guillermo Rigondeaux, 54 kg, who won two of Cuba's four gold medals at the last Games in Sydney.
For Kindelan, 31, who has fought 332 bouts and been defeated only 22 times, Athens will be his last Games, and he plans to retire from boxing to become a gym trainer in Cuba.
Rigondeaux, 23, was unbeaten in 134 fights from 1996 until he lost the world championship title last year, but he has suffered only 12 career defeats against 318 victories.
"I hit with both hands. Cuban boxing is more technique than force," he said.
Lorenzo Aragon, 69 kg, is the world champion and Cuba's most experienced fighter, with 420 bouts under his belt. He did not make the Sydney Games, but is ready to face any challenge in Athens and does not plan to come home empty-handed.
"There is no difficult rival when you are well trained. We train physically and ideologically and that prepares us to face any enemy or obstacle in our path", he said.